Variable phase shift selector



April 28, 1964 F. T. PITTs ETAL VARIABLE PHASE SHIFT SELECTOR Filed June29, 1962 United States Patent Office 3,131,367 Patented Apr. 28, 19643,131,367 VARIABLE PHASE SHIFT SELECTOR Fred T. Pitts, Rockville, andTommy S. Weaver, Arnold, Md., assignors, by mesne assignments, to theUnited States of America as represented by the Secretary of the NavyFiled .Tune 29, 1962, Ser. No. 207,169 1 Claim. (Cl. 333-31) The presentinvention relates to a phase shifter selector and more particularly to aVariable phase shifter selector that will rapidly select or 180 relativephase.

Various devices and schemes have been employed in the past for selectinga relative phase shift of a transmitted signal wave. In one method, theinput power is divided equally into two lines, one of which is anintegral number of half wavelengths (180 electrical degrees) longer thanthe other. The appropriate shift of either 0 or 180 electrical degreesis accomplished by means of switches, one of which is in each line. Thismethod, however, has several inherent disadvantages. For one thing,there is considerable power loss in such a device, and also, the use ofisolators is required. Furthermore, there is considerable difficulty inachieving phase accuracy.

In the present invention, a pair of transmission lines are providedbetween an input connector and an output connector with one transmissionline being a half wavelength longer than the length of the othertransmission line. A diode switch is provided in each transmission lineand the lengths of each line between the input connector and the diodesare integral numbers of half wavelengths. Thus each switch, when off,will present an open circuit at the input point and thus not introduceany shunt reactance on the selected line. Therefore, it is possible toeliminate the power divider and the isolators. In order to avoidextremely close tolerances on the mechanical parts of the selector, thephase shifter selector is made variable by providing a movable trimmerbar for one of the transmission lines.

It is therefore a general object of the present invention to provide animproved phase .shift selector.

Another object of the present invention is to provide an improvedselector for selecting either 0 or 180 degrees relative phase shift -ofa transmitted signal wave.

Still another object of the present invention is to provide a relativephase shift selector that has an extremely fast switching time.

Yet another object of the present invention is to provide an improvedphase shifter that is simple to manufacture and has a minimum number ofparts.

Other objects and advantages of the present invention will be readilyappreciated as the same becomes better understood by reference to thefollowing detailed description when considered in connection with theaccompanying drawing in which like reference numerals designate likeparts throughout the figures thereof and where- 1n:

FIGURE 1 is a diagrammatic View of one type of phase shift selector;

FIGURE 2 is a diagrammatic view of a preferred embodiment of t-hepresent invention; and

FIGURE 3 is an isometric view of a preferred embodiment of the presentinvention.

Referring now to the drawing, there is shown in FIG- URE 1, a powerdivider 11 having an input line 12 and two transmission lines 13 and 14connected thereto. Transmission line 14 is an integral number of halfwavelengths (180 electrical degrees) longer than transmission line 13.Isolators 15 and 16 are provided in lines 13 and 14, respectively. Also,switches 17 and 18 are provided in lines 13 and 14, as shown, and thetwo transmission lines are connected to a single output line 19.

In operation of the embodiment shown in FIGURE 1 of the drawing, inputpower is divided equally by the power divider 11 into each of thetransmission lines 13 and 14. With switch 18 in the open position andswitch 17 in a closed position, the power being transmitted throughtransmission line 13 has a relative phase shift of zero degrees at theoutput line 19. When it is desired to provide a relative phase shift ofdegrees, switch 17 is opened and switch 18 is closed, and the inputpower is transmitted from power divider 11 through transmission line 14to output line 19.

Referring now to FIGURES 2 and 3 of the drawing, which show a preferredembodiment of the present invention, there is shown an input connector21 and an output connector 22 to which transmission lines 23 and 24 areconnected. Connectors 21 and 22 might be of the coaxial type, and aresupported by a suitable frame or housing 25. Transmission lines 23 and24 are supported by suitable cross-braces 26 and 27, which can besecured to frame 25. Switches 28 and 29 are provided in transmissionlines 23 and 24, respectively. By Way of example, switch 28 might becomprised of crystal diodes 31 and 32 which are connected to a biaspulse source through connector 33; and likewise switch 29 might becomprised of crystals diodes 34 and 35 that are connected to a biaspulse source through connector 36. As shown in FIGURE 2 of the drawings,the distance between input connector 21 and switch 28 is equal to anintegral number of half wavelengths, and the distance between inputconnector 21 and switch 29 is one half wavelength longer than thedistance between input connector 21 and switch 28. A trimmer bar 37, ofsuitable metal, is provided near transmission line 24, and this bar 37is threadedly engaged with shaft 38 that is provided with a knob 39.Trimmer bar 37 is provided with a pair of feet 41 and 42 that slidablyengage with transmission line 24 in order to prevent rotation of trimmerbar 37 when knob 39 is rotated.

In operation of the embodiment shown in FIGURES 2 and 3 of the drawing,when switch 28 is in a closed position and switch 29 is in an openposition, an input signal wave at input connector 21 will be transmittedthrough transmission line 23 to output connector 22. The transmittedsignal will have a relative phase shift of zero degrees. When it isdesired to provide a relative phase shift of 180 degrees, switch 28 isopened and switch 29 is closed, and the input signal is transmitted frominput connector 21 through transmission line 24 to output connector 22.As the accuracy of the phase shift is a function of the length oftransmission line 24, trimmer bar 37 is provided to adjust the effectivelengt-h of transmission line. As handwheel 39 is rotated and trimmer bar37 is moved nearer to transmission line 23, the effective length oftransmission line 23 is shortened, and likewise, when trimmer bar 37 ismoved away from transmission line 37 the effective length oftransmission line 23 is lengthened.

The diodes in switches 28 and 29 are polarized such that the applicationof a bias pulse at a common point Will energize one switch. That is, abias pulse applied at connector 33 will energize diodes 31 and 32 and abias pulse applied at connector 36 will energize diodes 34 and 35.Direct current returns for the diodes consist of quarter wavelengthshort circuits which are assembled into the input and output connectors.

It can thus be seen that the present invention provides an improvedphase shifter selector that will rapidly select one of two relativephases.

While there has been described a preferred embodiment of the presentinvention, it will be obvious to those skilled in the art that variouschanges and modifications may be made therein without departing from thescope of the invention and it is to be understood, that within the scopeof the appended claims, the invention may be practiced otherwise than asspecifically described.

What is claimed is: A variable phase shift selector comprising: an inputconnector, an output connector, a first transmission line ofpredetermined length, a second transmission line having a length whichis a half wavelength longer than the length of said first transmissionline, i rst and second crystal diode switches connected one each in eachsaid transmission line, said first crystal diode switch being connectedan integral number of wavelengths from said input connector and saidsecond switch being connected an integral number `of References Cited inthe le of this patent UNITED STATES PATENTS Dicke May 15, 1955 Wright etal, Apr. 22, 1958 Arditi Sept. 30, 1958 Grieg et al. Aug. 30, 1960 PanSept. 6, 1960 Pritchard July 4, 1961 Ring May 1, 1962

